Campbell
Relaxed Intensity
All editions of D&D, Call of Cthulhu, Cyberpunk, Shadowrun, Marvel FASERIP, classic Deadlands, and WEG Star Wars are not the same game with minor variations.
My experience is that the core gameplay of many of these games does not significantly vary. Different sorts of fiction, but at the end of the day we are dealing with teams of specialists going on adventures presented to them by the GM. In the grand scheme of things playing Shadowrun, Legend of the Five Rings or sometimes even Vampire often did not feel that different from D&D because the core activity and structure of play was not that different.
I likely made my case too strongly. What I would say is that the adventure game subset of roleplaying games is much more akin to area control boardgames than it is boardgames.